Powder coating system and method for quick color change

ABSTRACT

A powder coating system includes a booth and one or more powder-recovery modules that are insertable into an equipment-receiving space of the booth. A color change method includes removing a first powder-recovery module from the equipment-receiving space and positioning a second powder-recovery module in the equipment-receiving space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. Ser. No. 09/982,761filed Oct. 18, 2001, now abandoned, the disclosure of which is herebyincorporated herein by reference. This patent application claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Patent ApplicationSer. No. 60/242,937, filed Oct. 24, 2000, the disclosure of which ishereby incorporated herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a powder coating system andparticularly, to a color change booth used in a powder coating system.More particularly, the present invention relates to a color change boothconfigured to permit recovery of powder that fails to adhere to objectsbeing coated in the booth.

Powder coating systems that operate to apply a coating ofelectrostatically charged particles or powder to an object are known. Atypical powder coating systems includes a booth through which objects tobe coated with powder are conveyed and one or more powder applicatorsthat spray electrostatically charged powder toward the objects to becoated. Some of the particles adhere to the object and some do not.Because powder is fairly expensive, it is desirable to recover thenon-adherent powder for re-use in the powder coating system.

Powder is available in a variety of colors. When manufacturers changethe color of powder being dispensed by the powder applicator(s), variouscomponents of the powder coating system need to be cleaned if powder isbeing recovered in such a way that powder of one color is notinadvertently contaminated with powder of another color so that it canbe reused. It is also highly desirable for the color change process tobe completed quickly to maximize utilization of the powder coatingsystem.

According to this disclosure, a powder coating system for coatingobjects with powder includes a separator assembly configured to removepowder from an air-powder mixture and a booth in which objects arecoated with powder. The booth has a bottom wall that overlies theseparator. The bottom wall is formed to include an opening through whichthe air-powder mixture moves into the separator assembly. The powdercoating system also includes a hopper assembly that underlies theseparator assembly. The powder removed from the air-powder mixture inthe separator assembly is fed downwardly to the hopper assembly.

In an illustrative embodiment, the hopper assembly includes a set ofwheels that allows the hopper assembly to be wheeled out from under thebottom wall and the separator assembly is carried by the hopperassembly. Air circulation equipment is included in the powder coatingsystem and operates to draw the air-powder mixture downwardly from thebooth and into separator assembly. The powder coating system includespowder applicators that spray powder to coat the objects and a powderstation that supplies powder to the powder applicators. Powder that isrecovered from the air-powder mixture and fed to the hopper assembly istransferred to the powder station for re-use.

Also according to this disclosure, the powder coating system includes aplurality of powder-recovery modules, each of which is interchangeablyinsertable into the equipment-receiving space to receive the air-powdermixture. Each illustrative powder-recovery module includes a separatorassembly and a hopper assembly. When the powder coating system ischanged over from coating objects with powder of a first color tocoating objects with powder of a second color, a first of the pluralityof powder-recovery modules is removed from the equipment-receiving spaceand a second of the plurality of powder-recovery modules is positionedin the equipment receiving space.

According to this disclosure, after any one of the powder-recoverymodules are removed from the equipment-receiving space during colorchanges, the removed powder-recovery module is disassembled and cleaned.Other portions of the powder coating system are cleaned during colorchange operations. In the illustrative embodiment, the powder coatingsystem is designed to permit two workers or operators to complete thecolor change process in 15 minutes or less.

Additional features of the invention will become apparent to thoseskilled in the art upon consideration of the following detaileddescription of a preferred embodiment exemplifying the best mode ofcarrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdetailed description and accompanying drawings which illustrate theinvention. In the drawings:

FIG. 1 illustrates a perspective view of a color change systemconstructed according to the invention showing multiple powder-recoverymodules or carts and a spray-to-waste module or cart, all orientedside-by-side near a color change booth and showing a thirdpowder-recovery module or cart situated in an equipment-receiving spaceof the booth;

FIG. 2 illustrates a top plan view of the system illustrated in FIG. 1;

FIG. 3 illustrates a partly fragmentary front elevation view of aportion of the powder coating system illustrated in FIGS. 1-2, showingthe booth, a powder station to the right of the booth, and aircirculation equipment to the left of the booth;

FIG. 4 illustrates a partly exploded perspective view of one of thepowder-recovery carts illustrated in FIG. 1, showing a wheeled hopperassembly, a separator assembly above the hopper assembly, and first andsecond ducts situated along opposite sides of the separator assembly;

FIG. 5 illustrates a perspective view of the hopper assembly illustratedin FIG. 4, showing venturi pumps coupled to the bottoms of respectivehoppers of the hopper assembly;

FIG. 6 illustrates a fragmentary perspective view of a detail of thebooth and powder-recovery cart illustrated in FIG. 1, showing the hopperassembly including a plate to which a number of hoses are coupled and acontrol panel for the booth;

FIG. 7 illustrates an enlarged fragmentary perspective view of a detailof the separator assembly illustrated in FIG. 4, showing an air-powdermixture entering a plurality of separator tube assemblies, a quantity ofrecovered powder moving downwardly out of the separator tube assemblies,and air that is generally powder-free moving upwardly out of the powdertube assemblies;

FIG. 8 illustrates a fragmentary perspective view of portions of thebooth and one of the powder-recovery carts illustrated in FIG. 1,showing the booth including lift rails supported relative to a frame ofthe booth by lift actuators. The powder-recovery cart including a pairof catch lips aligned with respective lift rails The powder-recoverycart is illustrated arranged for movement into an equipment-receivingspace of the booth;

FIG. 9 illustrates a fragmentary front elevation view of a portion ofthe booth and one of the powder-recovery carts. The cart is illustratedreceived in the equipment-receiving space of the booth. The wheels ofthe cart are illustrated resting on the floor. The upper surfaces of theducts are spaced apart from a bottom wall of the booth;

FIG. 10 illustrates a fragmentary front elevation view similar to FIG. 9showing the lift actuators actuated to lift the powder-recovery cart sothat the wheels of the cart are spaced apart from the floor and so thatthe upper surfaces of the ducts engage an undersurface of the bottomwall;

FIG. 11 illustrates a fragmentary sectional view of a portion of thebooth and one of the powder-recovery carts, taken generally alongsection lines 11—11 of FIG. 10. FIG. 11 illustrates the air-powdermixture moving downwardly from an inner space of the booth into theseparator assembly, recovered powder moving downwardly from theseparator assembly into the hopper assembly, and air moving upwardlyfrom the separator assembly into an air duct of the booth that overliesthe separator assembly;

FIG. 12 illustrates a fragmentary sectional view of a portion of thebooth showing doors in the bottom of the booth in open orientations,uncovering openings in the bottom wall of the booth;

FIG. 13 illustrates an enlarged sectional view of certain details ofFIG. 12 showing one of the doors moved by its actuator to a closedorientation to facilitate movement of workers around on the floor of thebooth;

FIG. 14 illustrates a fragmentary perspective view of a portion of thebooth and one of the powder-recovery carts showing a sensor on the boothhaving a lever which protrudes into the equipment-receiving space toserve entry of a powder recovery cart into the space;

FIG. 15 illustrates a perspective view similar to FIG. 14 showing thepowder-recovery cart moved into the equipment-receiving space. The leveron the sensor is actuated, signaling the presence of the powder-recoverycart in the equipment-receiving space;

FIG. 16 illustrates a fragmentary perspective view of a portion of apowder-management booth showing a container of powder sitting on a shelfof the booth, a plurality of suction tubes in a lowered orientation toextract powder from the container for delivery to the powderapplicators, a sieve having a frustoconical upper portion that receivesrecovered powder from the powder-recovery cart, and a hose extendingfrom a frustoconical lower portion of the sieve to the container todeliver recovered powder to the container;

FIG. 17 illustrates a fragmentary perspective view of the samecomponents as to FIG. 16 showing the plurality of suction tubes in araised orientation to permit removal and replacement of the powdercontainer. The lower end of the hose that extends from the sieve isillustrated removed from the container. The container is illustratedmoved off of the shelf to expose an array of air nozzles; and

FIG. 18 illustrates a fragmentary perspective view of some of the samecomponents as FIGS. 16-17, showing the suction tubes engaging the airnozzles. Air is provided from the nozzles to the suction tubes and otherpassages in the powder applicators to clean these components of powderduring color change operations. Components of the sieve are illustrateddisassembled to permit cleaning of the sieve components, for example,with an air gun during a color change operation.

DETAILED DESCRIPTIONS OF ILLUSTRATIVE EMBODIMENTS

A powder coating system 30 includes a color change booth 10 in whichobjects 26 are coated with particles of powder 28. Powder coating system30 also includes powder-recovery modules or carts 54 that are eachindividually insertable into an equipment-receiving space 24 provided bybooth 10. Powder coating system 30 further includes a powder station300, best illustrated in FIGS. 2 and 3, and powder applicators 42, bestillustrated in FIGS. 1-3. Powder applicators 42 can be of any of amember of known types that electrostatically charge and spray powder 28provided from powder station 300 toward objects 26 in booth 10. Aircirculation equipment 258 of powder coating system 30 operates to createan air stream that flows through booth 10 and the cart 54 received inspace 24. Some of the sprayed powder 28 adheres to objects 26 and somedoesn't. The non-adherent powder 28 that becomes entrained in the airstream flowing through booth 10 forms an air-powder mixture 29.Air-powder mixture 29 flows from booth 10 into the powder-recovery cart54 received in space 24 where powder 28 is separated from air-powdermixture 29 and returned to powder station 300 for reuse. When powdercoating system 30 is changed from coating objects 26 with powder 28 of afirst color to coating objects 26 with powder 28 of a second color, thecart 54 which has been used in the recovery of the powder 28 of thefirst color is exchanged for another cart 54 which will be used in therecovery of the powder 28 of the second color, and various components ofpowder coating system 30 are cleaned so that powder 28 of the firstcolor is not inadvertently mixed with powder 28 of the second color.

Illustrative color change booth 10 includes a top wall 12, side walls14, end walls 16, and a bottom wall 18 as shown in FIG. 1. Side walls 14and end walls 16 extend substantially vertically between top wall 12 andbottom wall 18. In addition, side walls 14 blend together with end walls16 to define rounded corner regions of illustrative booth 10. Booth 10,therefore, includes a plurality of walls 12, 14, 16, 18 that define aninterior 20. Booth 10 includes a frame 22, a portion of which ispositioned to lie beneath bottom wall 18, as best illustrated in FIG. 1.Frame 22 rests upon a floor and supports bottom wall 18 in spaced apartrelation from the floor so that equipment-receiving space 24 is definedbetween bottom wall 18 and the floor.

By blending walls 14, 16 together at rounded corner regions ofillustrative booth 10, the tendency of powder 28 to accumulate in theseregions is less than if walls 14 and walls 16 intersected at sharpercorners. However, it is within the scope of this disclosure for booth 10to have walls 12, 14, 16, 18 that meet at sharp or blended corners. Inaddition, it is within the scope of this disclosure for walls 12, 14,16, 18 to be made from any type of material having suitable structuralrigidity. However the tendency of powder to accumulate on walls 12, 14,16 is lessened if walls 12, 14, 16 are made from a non-metallicmaterial, such as a transparent resin. In the illustrated embodiment,bottom wall 18 is constructed from a stainless steel material, and thatattracts nonadherent, electrostatically charged powder 28 downwardlytoward it.

Objects 26 are supported 32 from an overhead conveyor 34 as bestillustrated in FIG. 1. Uncoated objects 26 are moved by conveyor 34 intointerior space 20 of booth 10 where powder 28 is dispensed onto theobjects 26. The objects 26 then continue on conveyor 34 out of interiorspace 20 of booth 10. Top wall 12 of booth 10 includes an elongated slot36 and end walls 16 include openings 38 that accommodates the supports32 by which objects 26 are transported through interior 20.

As objects 26 move into interior 20 of booth 10 prior to coating,supports 32 enter slot 36 at the front end thereof and objects 26 movethrough opening 38 in front end wall 16. As objects 26 move throughinterior 20 of booth 10 to be coated, supports 32 move through slot 36from the front end thereof to the rear end thereof while carrying theassociated objects 26 through the interior 20 of booth 10 to the rear ofbooth 10. After objects 26 are powder coated, objects 26 exit booth 10through opening 38 in rear end wall 16 and supports 32 exit slot 36 atthe rear end thereof. Booth 10 includes doors 40 that are movablebetween open orientations illustrated in FIG. 1, and closed orientations(not shown).

Powder coating system 30 includes one or more powder applicators 42 asillustrated in FIGS. 1 and 2. Each applicator 42 includes an in/outpositioner 50, reciprocator 44 carried by positioner 50, supports 46carried by reciprocator 44, and powder spray guns 48 mounted on thedistal ends of supports 46. Side walls 14 of booth 10 are formed toinclude one or more vertical slots 52, best illustrated in FIG. 12.Supports 46 extend from the associated reciprocator 44 through slots 52so that guns 48 are supported in the interior 20 of booth 10.

When objects 26 are being coated with powder 28, reciprocators 44operate under automatic control, which typically causes guns 48 toreciprocate up and down while electrostatically charged powder 28 issprayed from guns 48 toward objects 26. Movement of guns 48 in thismanner causes the cloud of powder 28 formed in interior 20 to berelatively more uniform, which promotes more even coating of objects 26.In some embodiments, reciprocators 44 also reciprocate guns 48 from sideto side. Positioners 50 also typically operate under automatic controlto project and retract associated reciprocators 44 and guns 48horizontally in and out relative to booth 10. Such horizontal in and outpositioning is desirable, for example, during cleaning operations and tocompensate for changing widths of objects 26 that are being powdercoated. Powder coating system 30 includes one or more control units 54which typically include computers, programmable logic controllers, orthe like that control the operation of reciprocators 44, positioners 50,and guns 48. Control units 54 are illustrated diagrammatically in FIG.2.

It will be appreciated that many different types of reciprocators,positioners, and guns may be used in powder coating system 30. Forexample, ITW Gema of Indianapolis, Ind. manufactures model no. ACR andZA 1 reciprocators; a model no. XT-6 positioner, and model no. PG-2A andmodel no. PG-2AX guns, all of which are suitable for use in such powdercoating systems 30. It is also within the scope of this disclosure forstationary guns that spray powder toward objects 26 to be included inpowder coating system 30 in lieu of, or in addition to, applicators 42.Such stationary guns or nozzles can be mounted to booth 10 or to othersupporting structure situated alongside booth 10. It will also beappreciated that minimizing the surface area of walls 12, 14, 16, 18 onwhich powder 28 can accumulate reduces the amount of time it takes toclean walls 12, 14, 16, 18 during color change operations.

Illustrative booth 10 does not include any manual powder applicatorequipment. To the extent that manual powder coating operations arerequired for any of objects 26, it is contemplated that such manualpowder coating operations be conducted in a separate spray-to-wastebooth (not shown) that does not need to be cleaned during color changeoperations. Of course, manual powder coating equipment can be includedin booth 10, if desired. Therefore, the present disclosure is notlimited to booths having only automatic powder coating equipment.

Powder coating system 30 includes multiple mobile powder-recoverymodules or carts 54, each of which is configured to be received inequipment-receiving space 24, as best illustrated in FIGS. 1 and 2. Whenit is received in equipment-receiving space 24, one of thepowder-recovery carts 54 functions to recover powder 28 from theentraining air stream 29 that enters the cart 54 from interior 20. Whenpowder coating system 30 is changed from coating objects 26 with powder28 of a first color to coating objects 26 with powder 28 of a secondcolor, the cart 54 received in equipment-receiving space 28 to separatepowder 28 of the first color from the associated air-powder mixture 29is moved out of equipment-receiving space 24 and another cart 54assigned to separate powder 28 of the second color from an entrainingair stream 29 is moved into equipment-receiving space 24. Thus, carts 54are exchanged during color change operations.

Turning now to the construction of carts 54, and with particularreference to FIGS. 4-11 and 14-16, each cart 54 includes a hopperassembly 56, a separator assembly 58 carried by hopper assembly 56, and60 that couple to separator assembly 58 as illustrated, for example, inFIG. 4. Carts 54 are modular. That is, associated hopper assemblies 56,separator assemblies 58, and ducts 60 are transportable together as aunit and are movable into and out of space 24 as a unit. Therefore, thedescriptions that follow of the hopper assembly 56, separator assembly58, and ducts 60 of one illustrative cart 54 apply to other carts 54 aswell, unless specifically noted otherwise.

Illustrative hopper assembly 56 includes an upper frame 76 having a pairof longitudinally extending side frame members 78 and a pair oftransversely extending end frame members 80 as illustrated in FIGS. 4and 5. Frame members 78 cooperate with frame members 80 to define arectangle. Frame 76 also includes four struts 74 that extend generallyparallel to frame members 80 between frame members 78 struts 74 aresubstantially uniformly spaced between frame members 80. Illustrativehopper assembly 56 also includes large hoppers 62 and a small hopper 64situated between hoppers 62/See FIG. 11. Hoppers 62, 64 extenddownwardly from an underside of frame 76.

Hoppers 62, 64 have side walls 66 that are generally triangular in shapeand end walls 68 that are generally trapezoidal in shape. Each ofhoppers 62, 64 includes a generally vertical by extending upper lip 67by which that hopper 62, 64 is mounted to frame 76. Surrounding lip 67of each hopper 62 thus defines a somewhat square-shaped openings 70 andlip 67 of hopper 64 defines a somewhat rectangular opening 71. Hoppers62, 64 thus define within their interiors powder-collection chambers 72,best illustrated in FIG. 11, beneath respective openings 70, 71. Two ofstruts 74 extend across respective openings 70 and two of struts 74 liebetween respective openings 70 and opening 71 as best illustrated inFIGS. 4 and 5.

Hopper assembly 56 includes four legs 82, two of which extend downwardlyfrom end wall 68 associated with hopper 62 at the front end of hopperassembly 56 and two of which extend downwardly from end wall 68associated with hopper 62 at the rear end of hopper assembly 56. Thelower ends of respective legs 82 are provided with casters 84 asillustrated, for example, in FIG. 4. Hopper assembly 56 also includes ahandle 86 connected by arms 88 to the two of legs 82 at the front end ofhopper assembly 56. Thus, powder-recovery carts 54 are made mobile andare easily movable around a powder coating facility.

Hopper assembly 56 includes a longitudinally extending channel member 90mounted to side walls 66 of hoppers 62, 64 as best illustrated in FIG.4. A vibrator 92, such as an eccentric motor, is mounted to member 90and is operable to vibrate hoppers 62, 64 to facilitate movement ofpowder 28 collected in hoppers 28 to the bottoms of powder-collectionchambers 72. A vibrator 92 controller 94 is mounted to one of legs 82 atthe front end of hopper assembly 56. A power cable 96 extends fromcontroller 94 to a power source (not shown) in a conventional manner. Acontrol cable 98 extends between controller 94 and vibrator unit 92.Controller 94 turns vibrator unit 92 on and off and controls thefrequency with which vibrator unit 92 vibrates hoppers 62, 64.

The lower ends of walls 66 of hoppers 62, 64 include openings 100 asillustrated, for example, in FIG. 11. Each cart 54 includes a set ofpowder transfer units 110 mounted to the bottom ends of hoppers 62, 64as best illustrated in FIG. 5. Each powder transfer unit 110communicates with a respective powder-collection chambers 72 through arespective associated openings 100. Illustrative powder transfer units110 are venturi pumps. In other embodiments of cart 54, powder transferunits 110 may be any other types of devices capable of extracting therecovered powder 28 from chambers 72 and moving powder 28 back to powderstation 300. Illustrative hopper assembly 56 includes a set of outlettubes 112, illustrated in FIGS. 9 and 10, that couple respectiveopenings 100 to respective venturi pumps 110. Venturi pumps 110communicate with respective chambers 72 through associated tubes 112 andopenings 100.

Hopper assembly 56 includes a manifold plate 114 mounted at a convenientlocation on hopper assembly 56 as illustrated best in FIG. 6. Ahigh-pressure air inlet port 116 and powder tube ports 118 extend fromplate 114 as illustrated in FIGS. 4 and 6. A high-pressure air hose 120is coupled to port 116 to deliver high-pressure air from a pressuresource (not shown) to cart 54. A three-way splitter 124 on the back sideof plate 114 receives high-pressure air through port 116 and delivershigh-pressure air to associated air-delivery hoses 122 which extend fromsplitter 124 to respective venturi pumps 110. Hopper assembly 56 alsoincludes three powder-transfer hoses 126 that extend between outlets ofassociated venturi pumps 110 and respective powder tube ports 118.High-pressure air delivered to venturi pumps 110 via hoses 122 passesthrough venturi pumps 110 powder 28 accumulated in the bottoms ofchambers 72 for transport back to powder station 300. The constructionand operation of venturi pumps and dense phase conveyors is well knownto those skilled in the art.

Separator assembly 58 is situated above and is carried by hopperassembly 56. Frame 76 of hopper assembly 56 has upper surfaces that aresubstantially coplanar with upper surfaces of struts 74 as illustratedin FIGS. 4 and 5. Separator assembly 58 rests upon the upper surfaces offrame 76 and struts 74. Hopper assembly 56 includes a plurality of tabs128 extending upwardly from frame 76 to facilitate orienting andretention of separator assembly 58 on hopper assembly 56. Separatorassembly 58 receives air-powder mixture 29 from ducts 60, separatespowder 28 from air-powder mixture 29, and delivers the separated powder28 to chambers 72 for recovery.

Illustrative separator assembly 58 includes five, side-by-side separatormodules 130, as best illustrated in FIG. 4. Referring to FIGS. 4 and 7each module 130 includes an upper panel 132, a box 134 underlying panel132 in spaced-apart relation therewith, a plurality of supports 133connecting panel 132 and box 134 at corners thereof, and a plurality ofvertically extending separator tube assemblies 136 coupled to panel 132and box 134. Each box 134 includes a rectangular top wall 138, arectangular bottom wall 140, a pair of long walls 142, and a pair ofshort walls 144. Boxes 138 are sized so that when modules 130 arecarried by hopper assembly 56, walls 142 lie above respective struts 74or end frame members 80 and walls 144 lie above respective portions ofside frame members 78.

Each panel 132 is formed to include a plurality of openings 146 andupper ends of associated tube assemblies 136, sealingly engage anunderside of panel 132 in the regions around respective openings 146 asshown in FIG. 7. Top wall 138 of each box 134 is formed to include aplurality of openings 148, each of which receives a middle portion of arespective tube assembly 136, and bottom wall 140 of each box 134 isformed to include a plurality of openings 150, each of which receives alower portion of a respective tube assembly 136. Thus, each one ofopenings 148 is vertically aligned with an associated opening 146 and anassociated opening 150

Each separator tube assembly 136 includes a cylindrical upper tube 152and a lower tube 154. Each lower tube 154 includes a cylindrical upperportion and a frustoconical lower portion. The cylindrical upper portionof each lower tube 154 has a larger diameter than the associated uppertube 152 and a lower portion of each upper tube 152 is received in thecylindrical upper portion of a respective lower tube 154. Each separatortube assembly 136 further includes a plurality of deflecting vanes 156at the upper end of lower tube 154. Vanes 156 extend radially betweencorresponding tubes 152, 154 and maintain tubes 152, 154 together in acoaxial configuration. Upper edges 158 of vanes 156 are substantiallycoplanar with an upper ends 160 of respective lower tubes 154. Vanes 156terminate at lower edges 162 spaced from upper edges 158. Vanes 156 areconfigured to deflect the air-powder mixture 29 which encounters them ina somewhat spiral or helical flow which causes powder 28 from inair-powder mixture 29 to be thrown radially outwardly by centrifugalforce. Thus, separator tube assemblies 136 are sometime referred to ascyclone separators. Gravity then causes the separated powder 28 to dropdownwardly through the frustoconical lower portion of tubes 154 and outof openings 166 into hopper assembly 56. As powder 28 moves downwardly,the air from air-powder mixture 29 is recovered by being drawn upwardlythrough tubes 152 by air circulation equipment 258 as will be discussedin further detail below.

Illustrative separator assembly 58 includes five separator modules 130that are arranged in side-by-side relation so that long walls 142 ofadjacent boxes 134 confront one another. Frame members 78, 80 and struts74 support modules 130 above powder-collection chambers 72 so thatpowder 28 separated from air-powder mixture 29 by separator tubeassemblies 136 falls downwardly through openings 168 into the associatedchamber 72. The middle separator module 130 is situated above chamber 72defined within hopper 64. The two separator modules 130 in front of themiddle separator module 130 are situated above the front hopper 62 andthe two separator modules 130 to the rear of the middle separator module130 are situated above the rear hopper 62 as illustrated in FIG. 4.Gaskets or other suitable sealing members can be interposed betweenbottom walls 140 of boxes 134 and the corresponding struts 74 and framemembers 78, 80. Separator assembly 58 includes a pair of vertical,transversely extending end plates 168 that are situated at opposite endsof separator assembly 58 above top walls 138 of the boxes 134 of the twoend modules 130 as illustrated in FIG. 4. End plates 168 are configuredto close the opposite ends of the space defined between panels 132 andtop walls 138 of boxes 134 of the endmost separator modules 130. In someembodiments, gaskets or other suitable sealing members are interposedbetween end plates 168 and modules 130.

Ducts 60 each include an upwardly facing rectangular surface 170defining an inlet opening 172 and a vertically oriented rectangularsurface 174 defining an outlet opening 176 as illustrated best in FIG.4. Ducts 60 also each include a pair of end walls 178, a curved innerwall 180, and a curved outer wall 182. Walls 180, 182 extendlongitudinally of cart 54 between walls 178. Thus, walls 178, 180, 182of each duct 60 provide a curved passage between openings 172, 176.Separator assembly 58 includes a plurality of attachment devices, eachof which includes a first portion 184 mounted to a respective end wall178 of an associated duct 60 and a second portion 186 mounted to arespective end plate 168. Clamping assemblies 184, 186 selectivelycouple ducts 60 to separator assembly 58. When ducts 60 are coupled toseparator assembly 58, the curved passages of ducts 60 communicate withthe opposite sides of the space defined between panels 132 and top walls138 of boxes 134 of modules 130. Gaskets (not shown) or other suitablesealing members may be provided on each of rectangular surfaces 170,174.

Bottom wall 18 of booth 10 is formed to include a pair of elongatedopenings 188 as illustrated best in FIGS. 2, 3, 9, 10, 12 and 13.Interior 20 is in gas-flow communication with equipment-receiving space24 through openings 188. When powder-recovery carts 54 are received inspace 24, openings 172 of the associated ducts 60 are vertically alignedwith openings 188. Each of openings 188 is bounded by a front end oredge 192, a rear end or edge 194, and a pair of longitudinal sides oredges 196 that extend between front and rear edges 192, 194. Front edges192 of openings 188 are spaced apart from the front end of bottom wall18 and rear edges 192 of openings 188 are spaced apart from the rear endof bottom wall 18.

Booth 10 is configured so that slot 36 formed in top wall 12 is parallelwith openings 188 and over the middle region of bottom wall 18. Thus,objects 26 moving through interior 20 of booth 10 on supports 32 passgenerally over the middle region of bottom wall 18. Air circulationequipment 258 operates to create a downdraft on opposite side of objects26 so that a significant amount of the nonadherent powder 28 in booth 10is swept away downwardly through openings 188, ducts 60, and intohoppers 62, 64.

Referring now to FIGS. 1, 3 and 8-13 frame 22 of booth 10 includes apair of rectangular lower frame portions 198 each having a pair of sideframe members 200 and a front frame member 210 as shown in FIG. 1. Frame22 further includes a rear frame member 212 coupled to the rear ends ofside frame members 200. A middle portion of rear frame member 212bridges the space between frame portion 198 as illustrated in FIG. 8.Frame 22 also includes vertical frame members 214, each of which extendsupwardly from an outside corner of each frame portion 198 to supportwalls 12, 14, 16, 18. Leveling pads 216 are provided on frame portions198 at appropriate locations to level booth 10. Equipment receivingspace 24 is defined between frame portions 198 at the front of booth 10.

Booth 10 includes actuators 220 mounted by brackets 222 to associatedside frame members 200 as illustrated in FIG. 8. Booth 10 furtherincludes a pair of lift rails 224 mounted on respective pairs ofactuators 220. In the illustrative embodiment, actuators 220 arepneumatic piston-and-cylinder actuators which are supplied withcompressed gas and vented through pneumatic lines 230, as is well-knownto those skilled in the art. It will be appreciated that other types ofactuators 220, including electrically powered actuators, hydraulicactuators, motors, and other electromechanical devices in combinationwith transmission elements or linkages, may be used. Each lift rail 224includes a vertical first side surface 234 facing toward theequipment-receiving space 24, a vertical second side surface 235 facingaway from the center region of equipment receiving space 24, and aguiding surface 236 that angles outwardly from surface 234 toward thefront of booth 10. Side frame members 78 of hopper assembly 56 are eachformed to include a catch lip 238 that extends longitudinally of frame76. Each catch lip includes a top portion 240 extending laterallyoutwardly from frame 76 and a side portion 242 extending downwardly fromthe respective top portion 240.

As powder-recovery cart 54 initially moves into equipment-receivingspace 24 in the direction of arrow 243, FIG. 8, guiding surfaces 236help to guide cart 54 into proper alignment with booth 10. As cart 54moves further into space 24 in direction 243, catch lips 238 move overrespective lift rails 224. Legs 82 at the rear end of cart 54 engage themiddle portion of rear frame member 212 upon full insertion of cart 54into space 24. When cart 54 is fully inserted into space 24, openings172 of ducts 60 are vertically aligned underneath openings 188 in bottomwall 18.

Referring to FIGS. 3 and 9-12 booth 10 includes an air plenum or duct244 coupled to an underside of the middle region of bottom wall 18between openings 188. Air plenum 244 has a planar bottom surface 246.Air plenum 244 has a large opening formed in bottom surface 246 andseparator assembly 58 is situated beneath this large opening when cart54 is inserted fully into space 24. Air plenum 244 further includes aninclined front panel 248 and a rectangular-to-round transition ductsection 250. Inclined panel 248 is configured to provide a uniformlyincreasing cross sectional duct area toward duct section 250, therebypromoting laminar flow of air from the cart 54 as the air moves into andthrough plenum 244.

After cart 54 is fully inserted into space 24 underneath bottom wall 18of booth 10, actuators 220 are actuated to lift cart 54 upwardly intosealing engagement with booth 10. As actuators 220 move from theretracted positions to the extended positions, lift surfaces 232 ofrespective lift rails 224 come into contact with top portions 240 ofrespective catch lips 238 to lift cart 54 upwardly from a loweredposition, illustrated in FIG. 9, to a raised position, illustrated inFIGS. 10 and 11.

Initially, before a cart 54 is lifted into orientation to be connectedto booth 10 to recover powder, rectangular surfaces 170 of ducts 60 arespaced apart from bottom wall 18 by a small distance 252 (FIG. 9) andtop walls 138 of separator modules 130 are spaced apart from bottomsurface 246 of air duct 244 by a small distance 254. In someembodiments, distance 252 may be substantially the same as to distance254 so that, as actuators 220 raise cart 54, sealing engagement of ducts60 with bottom wall 18 and sealing engagement of separator assembly 56with surface 246 of air plenum 244 occurs simultaneously. In otherembodiments, gaskets having different thicknesses may be interposedbetween ducts 60 and bottom wall 18 on the one hand and between air duct244 and separator assembly 56 on the other hand, and distances 252, 254need not be substantially equivalent. In such embodiments, as actuators220 raise cart 54, sealing engagement between ducts 60 and bottom wall18 may occur either before or after sealing engagement between air duct244 and separator assembly 56 depending upon differences in thethicknesses of the gaskets or sealing members used. Thus, interposinggaskets or other suitable sealing members between booth 10 and cart 54permits distances 252, 254 to be different.

After cart 54 is lifted upwardly into engagement with booth 10, casters84 are spaced above the floor by a distance 256 (FIGS. 10 and 11).Distance 256 is substantially the same as whichever of distances 252,254 is smaller, because once cart 54 moves upwardly by an amountsufficient to close the smaller one of distances 252, 254, cart 54 isunable to move upwardly any further to close the larger of distances254. Of course, if distances 252, 254 are substantially equal, thendistance 256 will also be substantially equal to distances 252, 254.

Various gaskets or sealing members are typically interposed betweencertain elements of cart 54 and between certain portions of cart 54 andbooth 10. In embodiments having such gaskets or sealing members, thesemay be constructed from urethane, such as microcellular urethane, or asimilar material having appropriate resiliency and sealing properties.In addition, the gaskets or sealing members may include pressuresensitive adhesives on their contact surfaces. In such embodiments, thepressure sensitive adhesive enables the gasket to which it is applied tobe adhered to the associated portion of booth 10 or cart 54.

Powder coating system 30 includes air circulation equipment 258 that iscoupled to air plenum 244 of booth 10 by duct work 260 as illustrated inFIGS. 2 and 3. Air circulation equipment 258 includes a housing 261 anda fan 262 having a motor 263 at the top of housing 261. Fan 262 isturned by motor 261 to draw air into and through inner space 20 of booth10, into and through separator assembly 58 of powder-recovery cart 54,into and through air plenum 244 of booth 10, and into and through ductwork 260. Air indicated by arrows 264 being drawn into inner space 20 ofbooth 10 moves from outside of booth 10 and through slot 36 and openings38 as illustrated in FIG. 3.

As air 264 moves through inner space 20 of booth 10, powder 28 exitingfrom guns 48 which does not adhere to articles 26 becomes entrained inair 264 to form air-powder mixture 29. Air-powder mixture 29 is drawn byair circulation equipment 258 through openings 188 of bottom wall 18 andthrough openings 172 into ducts 60 and then through openings 176 intothe space defined between panels 132 and boxes 134 of separator modules130. As described above with regard to FIG. 7, air-powder mixture 29moves through openings 148 formed in top walls 138 of boxes 134 intoseparator tube assemblies 136 where powder 28 is separated fromair-powder mixture 29 and is fed downwardly to hopper assembly 56 forrecovery. Air from the air-powder mixture 29 that enters separator tubeassemblies 136 moves upwardly through tubes 152 as indicated by arrows266 in FIGS. 7 and 11 after powder 28 is separated therefrom.

Air circulation equipment 258 draws air 266 from air-powder mixture 29upwardly through tubes 152 and into air plenum 244 through openings 146formed in panels 132 of separator modules 130. It will be appreciatedthat, while separator tube assemblies 136 are configured to separate asignificant amount of powder 28 from air-powder mixture 29, a smallpercentage of powder 28 from air-powder mixture 29 may still beentrained in the air 266 that moves upwardly from tubes 154 into airplenum 244. Thus, the air 266 moving upwardly through tubes 154 ofseparator tube assemblies 136 and into air plenum 244 is generally, butnot completely, powder-free.

Air circulation equipment 258 draws air 266 through air plenum 244 andinto duct work 260. Once air 266 reaches air circulation equipment 258,air passes through a filter section 268 of air circulation equipment258. Filter section 268 has a set of filters 270 that, in someembodiments, are high-efficiency cartridge filters, such as HEPAfilters, capable of filtering 0.5 micron particles at 99.999%efficiency. Air circulation equipment 258 includes a cleaning systemthat, from time to time, directs blasts of high pressure air at filters270 to dislodge the powder 28 that accumulates in filters 270. Forexample, in one embodiment, each high-pressure air blast is about 0.1seconds in duration. The cleaning air blasts occur about every 15seconds during the operation of fan 262. The dislodged powder 28 fallsdownwardly to a waste hopper 277 of air circulation equipment 258 forcollection and disposal.

After air 266 is filtered by filters 270 in filter section 268, fan 262discharges the filtered air into a return duct 272 and moves thefiltered air to a final filter section 274. Final filter section 274includes a plurality of filters 276 that, in some embodiments, are ableto filter 0.5 micron particles at 95% efficiency. Even though filters270 in filter section 268 have very high efficiency, over a long periodof time, the efficiency of filters 270 may decrease such that somepowder 28 may find its way past filters 270. In addition, if any filter270 has a compromised seal or a rupture, then powder 28 entrained in theair will pass through filters 270. Thus, filters 276 in final filtersection 274 are configured to capture most of any powder 28 passingthrough filters 270 prior to discharge of the air back into the ambientenvironment.

As illustrated diagrammatically in FIG. 3, air circulation equipment 258can be positioned on one side of a wall 278 of a manufacturing facilityand many of the other pieces of equipment of powder recovery system 30,such as booth 10 and carts 54, are positioned on the other side of wall278. Wall 278 can provide a barrier to same of the noise generated byfan 262 and the cleaning system of air circulation equipment 258 fromreaching the area of the manufacturing facility in which booth 10resides.

Fan 262 normally operates to move a sufficient volume of air at asufficient rate into booth 10 to prevent powder 28 sprayed from guns 48from exiting booth 10 through slot 36 and openings 38. In addition,illustrative separator tube assemblies 136 operate at high efficienciesto separate powder 28 from air-powder mixture 29. In an illustrativesystem the volume flow rate of air-powder mixture 29 drawn into eachseparator tube assembly 136 is in the range of about 17 cubic feet perminute to about 21 cubic feet per minute. Illustrative separator modules130, each having 76 separator tube assemblies 136, separate a highpercentage of powder 28 from air-powder mixture 29 if about 1500 cubicfeet of air per minute is drawn through each module 130. Thus, in theillustrative embodiment in which carts 54 each have five separatormodules 130, fan 262 is selected to move about 7500 cubic feet of airper minute through booth 10 and cart 54. This air flow rate contains thepowder 28 sprayed from guns 48 in booth 10 and also separator modules130 to have efficiencies consistently greater than 95%.

Air circulation equipment 258 includes a number of gages, pressureswitches and sensors (not shown) to sense air velocities and pressuresat various points in the air flow passages of air circulation equipment258. Depending upon the velocities and pressures sensed, the speed atwhich motor 263 of fan 262 operates can be adjusted to maintain theappropriate volume flow rates of air flow throughout powder coatingsystem 30. In addition, if certain sensors sense that the pressure dropacross, for example, filters 270 or filters 276 exceeds a certainamount, a warning indicator, such as a light or an image on a displayscreen, may be activated to indicate that filters 270 or filters 276, asthe case may be, will soon need to be replaced. If the sensors sensethat the pressure drop across filters 270 or filters 276 is too great,which indicates a heightened risk that powder containment in booth 10may be lost, then a signal can be sent to shut down powder coatingsystem 30 altogether. If powder coating system 30 is shut down in thismanner, the reason for the shutdown can also be displayed on a displayscreen.

Powder 28 that is separated from air-powder mixture 29 by separatorassembly 58 and that accumulates in the bottom of chambers 72 of hoppers62, 64 is moved by powder transfer units 110, such as illustrativeventuri pumps 110, back to powder station 300 as described above.Illustrative powder coating system 30 includes a set of hoses 280 thatextend between cart 54 and powder station 300 as shown in FIG. 3. Firstends of each of hoses 280 are coupled to ports 118 extending from plate114 of the cart 54 situated in space 24. Powder station 300 includes asieve 310, illustrated in FIGS. 3 and 16-18. Second ends of hoses 280are coupled to sieve 310. Each of hoses 126 extending from illustrativeventuri pumps 110 communicates with a respective hose 280 through anassociated port 118.

Referring now to FIGS. 16-18, during a coating operation a container 312of powder 28 rests upon a shelf 314 of powder station 300. Powderstation 300 includes a hose 316 that extends from the bottom of sieve310. An open, distal end of hose 316 is placed in container 312. Powder28 that accumulates in chambers 72 of hoppers 62, 64 is moved by powdertransfer units 110 through hoses 126, through ports 118, through hoses280, through sieve 310, through hose 316 and is returned to container312. Sieve 310 includes a frustoconical upper portion 317, afrustoconical lower portion 319, a filter screen 318 that is interposedbetween portions 317, 319 as shown in FIG. 18, and a band 321 thatcouples portions 317, 319 together as shown in FIGS. 16 and 17. Filterscreen 318 is configured to permit particles of powder 28 to passtherethrough while blocking any foreign contaminants that are largerthan the screen mesh to prevent them from reaching container 312.Recovered powder 28 is then recycled back through powder applicators 42to coat objects 26.

As described previously, when powder coating system 30 is changed overfrom coating objects 26 with powder 28 of a first color to coatingobjects 26 with powder 28 of a second color, the cart 54 situated inequipment-receiving space 24 during powder coating operations with thepowder 28 of the first color (hereinafter “first cart 54”) is removedfrom space 24 and a new cart 54 (hereinafter “second cart 54”) is movedinto space 24. Prior to removal of first cart 54 from space 24, guns 48of powder applicators 42 are turned off to permit one or more operatorsto perform certain cleaning operations as described below. In addition,conveyor 34 is operated to clear objects 26 out of booth 10.

After guns 48 are turned off so that no more powder 28 is being sprayedinto booth 10, an operator uses a squeegee, dry mop, broom, or othersimilar device (not shown) to clear bottom wall 18 of loose powder 28 bysweeping powder 28 from bottom wall 18 into openings 188. During thisinitial cleaning operation, air circulation equipment 258 continues tooperate so that the powder swept through openings 188 into thepowder-recovery cart 54 thereunder is recovered. In addition, theoperator sweeping the powder 28 on bottom wall 18 into openings 188inserts the squeegee, broom, etc. into inner space 20 of booth 10through the opening 38 at the front of booth 10 while standing on thefloor in front of booth 10. After bottom wall 18 is cleared of loosepowder 28, air circulation equipment 258 is turned off and first cart 54is removed from space 24.

To remove first cart 54 from equipment-receiving space 24, actuators 220are moved from the extended positions to the retracted positions so thatfirst cart 54 is moved from the raised position, illustrated in FIGS. 10and 11, to the lowered position, illustrated in FIG. 9. After first cart54 is moved to the lowered position, hoses 120, 280 are disconnectedfrom respective ports 116, 118, power cable 96 is disconnected from thepower source, and first cart 54 is wheeled out of space 24 for cleaning.First cart 54 can be disassembled so that ducts 60, separator modules130, and hopper assembly 56 can be cleaned separately. Portions ofclamping devices 184, 186 are manipulated to permit disconnection ofducts 60 from separator assembly 58. After ducts 60 are disconnected,separator modules 130 can be lifted off of hopper assembly 56. Anypowder 28 on ducts 60, separator modules 130, and hopper assembly 58 canbe cleaned using various cleaning devices, including high pressure airguns, vacuum cleaners, and manual cleaning devices, such as cloths,brooms, mops, and the like.

Booth 10 includes a pair of doors 290, each of which is supported withrespect to bottom wall 18 for movement between a first position closinga respective opening 188, as illustrated in FIG. 13, and a secondposition away from the respective opening 188, as illustrated in FIG.12. Booth 10 includes longitudinally extending frame members 294 andhinges 292. Each hinge 292 includes a first hinge half 293 coupled tobottom wall 18 by a respective frame member 294 and a second hinge half295 coupled to a respective door 290. Each hinge half 295 is pinned toan associated hinge half 293 for pivoting movement about a correspondinglongitudinally extending pivot axis 296. Pivot axes 296 are parallelwith the longitudinal dimensions of respective openings 188.

Booth 10 further includes actuators 286 that operate to move doors 290between the first and second positions. In the illustrative embodiment,actuators 286 are pneumatic actuators, each having a cylindrical housing285 and a piston that projects and retracts a rod 287 out of and intothe associated housing 285 in a conventional manner when air is suppliedto or exhausted from the housing 285. Each actuator 286 is pivotablycoupled between a member 288 of frame 22 and an associated door 290.Movement of actuators 286 between extended positions and retractedpositions moves the respective doors 290 between the first and secondpositions.

It will be appreciated that other types of actuators, includingelectrically powered linear actuators, hydraulic actuators, motors, andother electromechanical devices in combination with transmissionelements or linkages, may be used in lieu of pneumatic actuators. Thus,the term “actuator” or “actuators” as used in the specification and inthe claims is intended to cover all of these types of actuators, as wellas the equivalents thereof unless otherwise specified.

Each door 290 includes a fillet 289 having an upper surface 291. Inaddition, each door 290 includes a portion 298 that offsets fillet 289away from hinge half 295 so that, when doors 290 move to the respectivesecond positions, fillets 289 move downwardly and outwardly away formthe central region of space 24 by a sufficient amount to accommodatereceipt of ducts 60 beneath openings 188. Fillets 289 are received inrespective openings 188, with the result that surfaces 291 of fillets289 are substantially coplanar with the upper surface of bottom wall 18when doors 290 are in the first positions as illustrated in FIG. 13.When doors 290 are in the first positions, fillets 289 fill almost allof the space bounded by edges 192, 194, 196 which define respectiveopenings 188. Sufficient clearance exists between fillets 289 and edges192, 194, 196 to facilitate the movement of doors 290 into their firstpositions.

After first cart 54 is removed from space 24 and doors 290 are moved tothe first positions to close openings 188, the operator enters booth 10through opening 38 at the rear of booth 10. Because walls 12, 14, 16, 18of booth 10 are elevated above the floor by frame 22, a set of stairs282 and a landing 284 at the top of stairs 282 are provided at the rearof booth 10 to facilitate the operator's entry into inner space 20 ofbooth 10. Stairs 282 and landing 284 are illustrated in FIG. 2. Afterthe operator enters inner space 20 of booth 10, doors 40 are moved tothe closed positions and the operator cleans the surfaces of walls 12,14, 16, 18 and doors 40 that face toward inner space 20 by vacuuming,mopping and the like. As illustrated in FIG. 13, receipt of fillets 289in openings 188 levels the bottom wall 18 when doors 290 are moved totheir closed positions.

Booth 10 includes a control panel 330, best illustrated in FIGS. 6, 14and 15, at the front end of booth 10 and a sensor 320, best illustratedin FIGS. 14 and 15, coupled to a frame member 322 behind control panel330. Control panel 330 includes a first switch 332 that controls theextension and retraction of actuators 220, a second switch 334 thatcontrols the extension and retraction of actuators 286, and a pressureregulator 336 that controls delivery of high pressure air through hose120, port 116, splitter 124, and hoses 122 to venturi pumps 110. Ahigh-pressure air port 338 is also provided on control panel 330 as aconnection point for various devices, such as high-pressure air guns(not shown), that require high pressure air for operation.

Pushing switch 332, moves actuators 220 to extended positions to raiselift rails 224. Pulling switch 332 outwardly moves actuators 220 toretracted positions to lower lift rails 224. When no cart 54 is presentin space 54, pushing switch 334 inwardly moves actuators 286 to extendedpositions to raise doors 290 to the first positions to close openings188. Pulling switch 336 outwardly moves actuators 286 to retractedpositions to move doors 290 away from openings 188. Adjusting pressureregulator 336 changes the pressure of air supplied to venturi pumps 110through hose 120, port 116, splitter 124, and hoses 122. Control panel330 includes a gauge 340 that provides a booth operator with a visualindication of the pressure being supplied to venturi pumps 110.

Sensor 320 senses the presence of a cart 54 in space 24. In theillustrative embodiment, sensor 320 has a lever 324 that is biased to asubstantially vertical orientation extending into equipment-receivingspace 24, as illustrated in FIG. 14. When a cart 54 is moved into space24, the cart 54 engages lever 324 moving it away from the verticalorientation, as illustrated in FIG. 15. When a cart 54 moves lever 324in this manner, a signal is provided to controller circuitry of booth 10that prevents movement of doors 290 from the second positions to thefirst positions. Thus, if switch 334 is pushed when a cart 54 is inspace 24, actuators 286 will not move from the retracted positions tothe extended positions.

After the operator finishes cleaning doors 40 and walls 12, 14, 16, 18in inner space 20 of booth 10, doors 40 are opened and the operatorexits booth 10. Then, after the operator exits booth 10 and beforesecond cart 54 is moved into space 24, switch 334 is pressed to movedoors 290 from the first positions to the second positions. Once doors290 are moved to the second positions, second cart 54 is pushed intospace 24. Switch 332 is pressed to raise second cart 54 into sealingengagement with booth 10. Hoses 120, 280 are connected to respectiveports 116, 118 of second cart 54, either before or after second cart 54is raised by actuators 220.

Various portions of powder station 300 and powder applicators 42 arecleaned when powder coating system 30 undergoes a color change. A secondoperator may attend to the cleaning of powder station 300 and powderapplicators 42 while the first operator cleans booth 10 and exchangescarts 54. Illustrative powder coating system 30 is designed to permittwo operators to complete the color change process in 15 minutes orless.

In the illustrative embodiment, many of the cleaning operations ofpowder station 300 and powder applicators 42 are done under automaticcontrol and therefore, the worker attending to the cleaning of thesepieces of powder-delivery equipment 42, 300 does so, in large part, byentering various cleaning commands via a user input device, such as acomputer keyboard or a touch-screen display. For example, such a userinput device 326 coupled to an upper portion of a housing 328 of powderstation 300 is illustrated diagrammatically in FIG. 3. When the operatorselects a cleaning mode by entering inputs on device 326, powderdelivery to guns 48 is stopped and the components of guns 48 that causepowder 28 to be electrostatically charged are turned off. Reciprocators44 and positioners 50 automatically move to cleaning positions. A numberof high-pressure air nozzles (not shown) are coupled to booth 10 in thevicinity of vertical slots 52. Positioners 50 move guns 48 cyclically inand out under automatic control while high-pressure air exits the highpressure air nozzles to blow off any powder 28 accumulated on theexternal surfaces of guns 48. Additional details of such high pressureair nozzles that clean guns 48 can be found in U.S. Pat. No. 5,759,271,which is incorporated by reference herein.

Returning again particularly to FIGS. 16-18, powder station 300 includesan assembly 342 of tubes 346 and a plurality of suction hoses 344 thatextend between the upper ends of tubes 346 and respective guns 48. Tubes346 that are provided in two groups mounted on respective stabilizingbars 348 as illustrated in FIGS. 17 and 18. Tube assembly 342 furtherincludes a lift bracket 350 coupled to the upper ends of tubes 346.

Powder station 300 includes a guide 352 and a lift assembly 354. Liftassembly 354 includes a pair of lift actuators 356 including cylinders358 coupled to guide 352 and rods 360 that extend and retract relativeto cylinders 358. Lift assembly 354 further includes a slider 362coupled to upper ends of rods 360. Bracket 350 is coupled to slider 362by flange 364. Slider 362 moves upwardly on guide structure 352 whenrods 360 are extended out of cylinders 358 and slider 362 movesdownwardly on guide structure 352 when rods 360 are retracted intocylinders 358. Flange 364, bracket 350, tubes 346, and bars 348 movewith slider 362 as slider moves upwardly and downwardly.

During powder coating operations, the lower ends of tubes 342 arelowered into the mass of powder 28 contained in container 312 andsuction is applied to tubes 342 and hoses 344 to extract powder 28 outof container 312 and deliver the extracted powder 28 to guns 48. Duringa color change operation, an operator enters a command on input device326 to lift tube assembly 342 upwardly out of container 312 as indicatedby arrow 366 in FIG. 17. After tube assembly 342 is lifted out ofcontainer 312, container 312 is removed from shelf 314. The operatorremoves the bottom end of hose 316 from container 312, and then removescontainer 312 from shelf 314.

Powder coating station 300 includes a plurality of high-pressure airnozzles 368, each of which is aligned with an opening in a correspondingtube 346 as illustrated in FIG. 17. Nozzles 368 are provided openings369 formed in shelf 314. The ends of nozzles 368 are eithersubstantially coplanar with or slightly below shelf 314. After container312 is removed from shelf 314, the operator enters a command on inputdevice 326 to lower tube assembly 342 downwardly from a raised position,illustrated in FIG. 17, to a lowered position, illustrated in FIG. 18.When tube assembly 342 is in the lowered position, each nozzle 368registers with opening in respective tube 346. Then, high-pressure airis supplied through nozzles 368 to clean powder 28 from the internalpassages of tubes 346, hoses 344, and guns 48. After a time, thehigh-pressure air is turned off and tube assembly 342 is lifted fromnozzles 368 to the raised position illustrated in FIG. 17.

While tubes 346, hoses 344, and guns 48 are being cleaned, the operatorcan disassemble sieve 310 and clean filter screen 318 and portions 317,319 using, for example, a high-pressure air gun 367, illustrated in FIG.18. If desired, after disconnection of hoses 280 from ports 118 of acart 54 and before removal of the end of hose 316 from container 312,the operator may insert air gun 367 into the ends of the hoses 280disconnected from ports 118 and direct high-pressure air through hoses280 to blow any powder 28 remaining in hoses 280 through sieve 310 andinto container 312. Alternatively, the operator may replace hoses 280with clean ones during color change operations and forego using air gun367 to clean the hoses 280 being replaced. The operator cleaning powderstation 300 may also will use a cloth or the like to wipe down externalsurfaces of the various pieces of equipment, such as sieve 310, tubeassembly, and lift assembly 354.

After powder station 300 is cleaned, a replacement container 312 thatcontains powder of a different color is placed on shelf 314 and theoperator enters a command on input device 326 to lower tube assembly 342into the replacement container 312. Then, once the operator cleaningpowder station 300 confirms that no one is in booth 10 and that booth 10and second cart 54 are ready for powder coating operations, the operatorenters commands on input device 326 to resume the powder coatingoperations.

Powder coating system 30 includes at least one spray-to-waste equipmentmodule or cart 370 as illustrated in FIGS. 1 and 2. Cart 370 is placedin equipment-receiving space 24 when no powder 28 is to be recovered forreuse during powder coating operations. Cart 370 is similar to carts 54and therefore, like reference numerals are used to denote components ofcart 370 that are substantially the same as like components of carts 54.The main difference between cart 370 and carts 54 is that cart 370 doesnot include any separators or hoppers.

Cart 370 includes a rectangular bottom panel 372 and a pair of endpanels 374 extending upwardly from bottom panel 372. Cart 370 furtherincludes a pair of frame members 376 extending longitudinally betweenthe upper corners of end panels 374 and a set of vertical frame members378 extending between frame members 376 and bottom panel 372 forstability. Ducts 60 are coupled to end panels 374 with clamping devicesthat are the same as the clamping devices used in carts 54 to coupleducts 60 to separator assembly 58. Cart 370 is configured so that anempty space 380 is defined above bottom panel 372 between end panels374. The inner passages of ducts 60 are in fluid-flow communication withempty space 380 through openings defined beneath frame members 376 andbetween frame members 378.

When cart 370 is received in space 24 and lifted to a raised position byactuators 220, empty space 380 is in fluid-flow communication with airplenum 244. In some embodiments, gaskets or sealing members areinterposed between bottom surface 246 of air plenum 244 and the uppersurfaces of frame members 376 and end panels 374 of cart 370.

When spray-to-waste cart 370 is received in space 24, the air powdermixture 29 is drawn by fan 262 through openings 188 formed in bottomwall 18 of booth 10, through ducts 60, through empty space 380 of cart370, through duct work 260, and into housing 261. After air-powdermixture 29 reaches housing 261, fans 262 draw air-powder mixture 29through filters 270 of filter section 274 so that powder 28 is filteredout of air-powder mixture 29. The powder 28 filtered out of air-powdermixture 29 is blown downwardly to waste hopper 277 by the cleaningsystem of air circulation equipment 258 for collection and disposal.When cart 370 is received in space 24, air circulation equipment 258 canbe operated to draw air through booth 10, cart 370, air plenum 244, andductwork 260 at a higher flow rate than when any of carts 54 arereceived in space 24.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of the invention as described and defined in thefollowing claims.

1. A powder coating system permitting for quick color changes, thepowder coating system operating to dispense powder onto objects to becoated by the powder and including a booth in which objects are orientedfor powder coating, the booth including a bottom wall beneath which isdefined an equipment-receiving space, the bottom wall including a pairof transversely spaced-apart openings through which an air-powdermixture moves from the booth, and a plurality of powder-recoverymodules, the powder-recovery modules being selectively andinterchangeably insertable into the equipment-receiving space to receivethe air-powder mixture through the openings, each of the powder recoverymodules including a pair of ducts, each duct of the pair of ducts forselectively engaging a respective one of the transversely spaced-apartopenings when a respective powder recovery module is oriented in theequipment receiving space to receive the air-powder mixture.
 2. Thepowder coating system of claim 1 wherein each of the powder-recoverymodules includes a hopper assembly and a separator assembly coupled tothe hopper assembly.
 3. The powder coating system of claim 2 whereineach of the powder-recovery modules includes wheels to facilitateselective and interchangeable insertion of the powder-recovery modulesinto the equipment-receiving space.
 4. The powder coating system ofclaim 2 wherein the separator assembly of each powder-recovery equipmentmodule is above a respective hopper assembly.
 5. The powder coatingsystem of claim 1 further including powder-delivery equipment forsupplying powder for coating objects, each of the powder-recoverymodules including powder-transfer equipment for transferring recoveredpowder from the respective powder-recovery module to the powder-deliveryequipment.
 6. The powder coating system of claim 5 wherein thepowder-transfer equipment includes a venturi pump.
 7. The powder coatingsystem of claim 5 wherein the powder-delivery equipment includes apowder dispenser for dispensing powder into the booth and a powderstation for receiving powder from the powder-recovery module received inthe equipment-receiving space and supplying the recovered powder to thepowder dispenser.
 8. The powder coating system of claim 7 furtherincluding a reciprocator, the powder dispenser coupled to thereciprocator to be reciprocated thereby.
 9. The powder coating system ofclaim 1 further including air circulation equipment for drawing theair-powder mixture from the booth, through the openings, and into thepowder-recovery module received in the equipment-receiving space. 10.The powder coating system of claim 9 wherein the air circulationequipment includes a filter, the air circulation equipment drawing theair-powder mixture from the booth, through the openings, and into thepowder-recovery module received in the equipment-receiving space, aircontaining unrecovered powder passing through the filter and filteredair then being discharged to atmosphere.
 11. The powder coating systemof claim 9 wherein the booth includes an air duct coupled to the bottomwall and the air duct provides a passage between the powder-recoverymodule received in the equipment-receiving space and the air circulationequipment.